<!DOCTYPE html>
<html>
<h>
    <meta charset="UTF-8">
    <title>字符串大小写转换</title>
</head>
<body>
    <script>
        var arr='www.jb51aITCASE.CN'
        document.write('原字符串为:'+arr+'<br>'+arr.toLocaleUpperCase()+'<br>'+arr.toLocaleLowerCase())
    </script>
</body>
</html>